1 ) Field of the Invention
The present invention relates to a plural liquid pack-type heat-curable resinous composition, and a process for producing a shaped resin article therefrom. More particularly, the present invention relates to a plural liquid pack type heat-curable resinous composition having a low viscosity, being curable at a relatively low temperature, having an excellent storage stability, handling properties and moldability, and being used for producing a shaped resin article having a superior heat resistance, chemical resistance, and mechanical strength, and relates to a process for producing a shaped resin article therefrom with high reproducibility and stability.
2) Background of the Invention
Due to recent technological developments, various new types of resinous materials having excellent heat resistance, mechanical properties, and moldability are now in demand.
Among these new resinous materials, the most noticeable is a reaction-molding type resin comprising a reactive monomer or oligomer. This reaction-molding type resinous material is a heat-curable resinous material having a relatively low viscosity, preferably being in the state of a liquid at room temperature, and capable of being simultaneously molded and cured (hardened or polymerized).
The heat-curable resinous materials include polyurethne resins, expoxy resins, unsaturated polyester resins, polyvinylester resins and polydicyclopentadtene resins. Some of the above-mentioned resinous materials already have been commercially produced and marketed.
These resins have, however, both merits and demerits, for example, a polyurethane resin has low heat resistance and unsatisfactorily low viscosity, because oligomers are used as the isocyanate and/or polyol components. An epoxy resin is superior to polyurethane in heat resistance, but its viscosity is high and the reactivity is not always satisfactorily high. An unsaturated polyester resin is hard and brittle, an epoxy(meth)acrylate is low in heat resistance, and both of them are not always low in viscosity.
Moreover, the urethane (meth)acrylates described in Japanese Patent Laid-open No. Tokkaisho 57-182312Specification (corresponding to U.S. Pat. No. 4,480,079) can lower its liquid viscosity by use of a reactive diluent, but suitable balance between its heat resistance, toughness, molding shrinkage and other properties are not well established.
Japanese Patent Publication No. Tokkosho 53-31515 discloses a process for producing a polymerizable resin which is characterized by reaction between a polyisocyanate and an acrylic ester or .beta.-alkylacrylic ester bearing an epoxy group. In the process, the isocyanate groups and the epoxy groups are preliminarily allowed to react whereby oxazolidone rings are formed to give a polymerizable resin, then a radical catalyst is added to polymerize the remaining vinyl groups to give a thermosetting resin. Thus, the polymerizable resin is unsuitable for reactive molding because of its high viscosity.
In the meantime, Japanese Patent Laid-open No. Tokkaisho 50-39400 discloses copolymerization of polyisocyanates with ethylenically unsaturated compounds. The product according to the process can lower the viscosity of the resin composition and give a cured resin of high heat resistance, but its toughness is not always high, giving a hard and ductile resin.
Japanese Patent Publication No. Tokkosho 61-31129 (corresponding to U.S. Pat. No. 4,162,357) describes a production process for a synthetic resin bearing isocyanurate rings by polymerization of a polyisocyanate including 2,4'-diisocyanate diphenylmethane in the presence of a polymerizable, olefinically unsaturated monomer, and/or an epoxy compound and/or a compound having hydrogen atoms reactive with isocyanates. But, the process according to the specification causes poor storage stability and troubles such as difficult molding because defoaming becomes impossible, when a catalyst system capable of curing within 1 second is used. All of the examples described in the above-stated Japanese Patent Publication No. Tokkyosho 61-31129 (corresponding to U.S. Pat. No. 4,162,357) contain epoxy compounds, but their reactivity is low and the epoxy groups remain unreacted unless they are exposed to a temperature higher than 140.degree. C. for more than a certain time, and adverse effects influence a variety of physical properties of the molded products and cause problems such as increased viscosity of the composition.